ABSTRACT
Afield trial was conducted in the 1991 wet season on the Research Farm of the Institute for Agricultural Research, Samaru, Zaria (11° 11'N, 7 38'E, 658m above mean sea - level) located in the northern Guinea savanna ecological zone of Nigeria . The objec iv e was to determine the effects of nitrogen and phosphorus on the productivity of maize and groundnut in mixture. Five levels of nitrogen (0, 40, 80, 120 and 160 kg N/ha) laid out in main plots and three levels of phosphorus (0, 2 6 . 4 , 5 2 . 8 kg P/ha) in sub plots were tested on the maize/groundnut mixture in all possible combinations in a split- plot d design. Application of 40 kg N/ha significantly increased maize shelling percentage, stover yield , cob diameter, LAI at 13 WAP, Plant and ear heights . Whereas application of 80 kg N/ha remarkably increased maize grain yield , 1000-grain weight and further increased stover yiel d and cob diameter. Maize kernel depth , cob length and cob number per plant increased with N level up to 80 kg N/ha. However application of 80 kg N/ha significantly reduced the number of days to 50% silking . Application of 26.4 k g P/h a significantly increased maize stover yield, LAI at 13 V/AP, but resulted in shorter days to 50% silking. Increasing P level to 52.8 kg P/ha appreciably i n c r e a s e d maize 1000-grain weight, cob d i a m e t e r , p l a nt and ear h e i g h t s and f u r t h e r i n c r e a s e d stover y i e l d , but reduced days to 50% t a s s e l i n g , However maize grain yieldbelling percentage, cob number per plant;, cob length, kernel depth, LAI at 10 WAP and percentage of lodged plants did not respond to P application. Application of nitrogen to maize in the mixture indirectly depressed groundnut pod and kernel yields, ' Haulm yield and number of mature pods per Plant, were significantly reduced by the application of 40-120 kg N/ha. The groundnut LAI at 10 and 13 WAP were also remarkably reduced by the application of 120 kg N/ha. However nitrogen application had no significant effect on groundnut shelling percentage, 100-kernel weight, number of immature pods per plant, plant height and days to 60% flowering. Application of phosphorus did not affect groundnut except the LAI at 10 WAP that increased. The highest LER of 1.35 and the highest cross returns less fertilizer cost was obtained from the application of 160application of 80 kg/ha + 0 kg P/hn was the lowest combined levels of N and P that gave significant increase in LER. Highest return per Nairn invested on fertilizer was obtained from the application of 40 kg N/h a with ou t phosphorus, followed by 80 kg N/ha + 0 kg P/ha. Given the condition of this study where there was appreciable soil P and considering the financial constraints of the small scale farmers who grow their crops mostly in mixture, application of 80 kg N/ha without P is most promising for the productivity of maize/groundnut mixture.
